1. Field of the Invention
This invention relates to a flywheel device applied, for example, to an uninterruptible power source device for a computer, etc., and more specifically, to a flywheel provided with an absorbing mechanism for absorbing rotating inertia energy of a flywheel rotor when the rotor rotating at a high speed malfunctions.
2. Description of the Prior Art
With the recent progress of electronic technology of computers and the like, uninterruptible power source devices provided with a battery or the like have been developed. One example so far proposed is a flywheel power source device or the like which utilizes a rotating inertia force of a flywheel to supply power to a load of a computer or the like, as a generator, when a momentary power failure occurs.
In a flywheel power source device applied to the aforesaid power source device or the like, as shown in FIG. 1, a casing 1 comprising a frame base 1a and a cover 1b interiorly supports a rotating shaft 3 of a rotary body 20 so that the shaft 3 may be rotated at a high speed, the rotary body 2 being composed of a flywheel 2a at the pper side thereof and a rotor 2b integrally formed at the lower side of the flywheel 2a. The rotating shaft 3 comprises a lower portion which consists of a spiral shaft 3a having a spherical surface at the lower portion thereof carried on a lower bearing 4 composed of a stationary portion 4a and a bearing portion 4b provided on the base 1a, and an upper portion which consists of an upper rotating shaft 3b carried on an upper bearing 5 provided on the cover 1b. A rotor magnet 6 is secured to the inner peripheral portion of the rotor 2b, and a stator 7 is provided oppositely of the rotor magnet 6 and in the outer periphery of a stationary portion 4a of the lower bearing 4. This stator 7 comprises a stationary core 7a and a stationary coil 7b.
WIth the arrangement as described above, the flywheel device normally acts as an electric motor so that when a voltage is applied from an external power source to coil 7b of the stator 7, the rotary body 2 comprising rotor 2b and flywheel 2a is rotated at a high speed in one or the other direction by means of an electromagnetic force produced in the rotor magnet 6 to store rotating energy. On the other hand, when the external power source device malfunctions, for example, an interruption of electric service occurs, the flywheel device acts as a generator so that power is supplied, for example, to a load of a computer or the like by the stator 7 according to the rotating energy stored in the rotor 2b of the rotary body 2, and the device is used as an interruption compensator. Accordingly, the flywheel needs to store a sufficient energy to cope with generation of an abnormal state of the power source. Therefore the rotor 2b rotates at a high speed.
However, according to the flywheel device constructed as described above, when the rotor 2b rotates at an abnormally high speed due to a malfunctions of for example a control device, the flywheel receives an abnormal centrifugal force and spreads in an outer peripheral direction. This causes the flywheel to come into contact with the cover 1b of the casing 1 or the like while being rotated at a high speed. This leads to problems such as occurrence of trouble internally of the device or breakage of parts in the device.
To eliminate these problems, a flywheel device as shown in FIG. 2 has been proposed. In FIG. 2, parts indicated by numerals 1 to 7 correspond to those of FIG. 1, description of which is therefore omitted. At a position opposed to the outer periheral surface of the rotor 2b in the inner peripheral surface of the cover 1b of the casing 1 is secured a protective ring 8 by means of a fixing means such as screws 9 ... with a gap G provided thereat, and a temperature sensor 10 is provided on the protective ring 8.
With the arrangement as described above, during the normal operation, the rotor 2b rotating at a high speed maintains substantially a uniform gap G relative to the inner peripheral surface of the protective ring 8. However, in the case where the rotation of the rotor 2b is a malfunctions and a deformation not less than the predetermined gap G occurs, the outer peripheral portion of the rotor 2b comes into contact with the inner peripheral portion of the protective ring 8. This contact-friction causes a braking force to act on the abnormal high speed rotation of the rotor 2b. Furthermore, frictional heat produced when the outer peripheral portion of the rotor 2b contacts the inner peripheral portion of the protective ring 8 is detected by the temperature sensor 10. When the value detected by the sensor 10 exceeds a reference value, the controller (not shown) actuates to cut off the power source to stop supply of power to the flywheel device to control the motor. The rotor 2b is controlled to be rotated at a low speed so as not to produce a breakage, damage or the like within the flywheel device.
However, the conventional flywheel device provided with the protective ring as mentioned above also has the following problems.
First, in the event that the rotor 2b at the lower side of the rotating body 2 is spread due to the centrifugal force resulting from the abnormal high speed rotation and comes into contact with the inner peripheral surface of the protective ring 8 with a great contact force, the outer peripheral portion of the spread rotor 2b partially strongly impinges upon the inner peripheral surface of the protective ring 8 or cuts thereinto. As a result, the protective ring 8 receives the action of the rotating energy of the rotating body 2 and tends to rotate. Therefore, a fixing portion between the inner peripheral surface of the cover 1b and the protective ring 8, for example, screws 9, a mounting hole, etc. are broken, which leads to a looseness or a play in mounting state of the protective ring 8 and failure to brake the rotating body.
Since in prior art, the rotational speed of the rotating body 2 has been controlled by sliding frictional heat between the rotor 1b and the protective ring 8, it is necessary to convert a detection signal of the temperature sensor 10 into a control signal or the like by means of a controller (not shown) or the like. Another problem has been encountered in that the circuit construction of the controller becomes complicated resulting in frequent troubles and complexity of maintenance and repair.